The embodiments herein relate generally to forming proppant-free channels in a proppant pack in subterranean formations.
Hydrocarbon producing wells (e.g., oil producing wells, gas producing wells, and the like) are often stimulated by hydraulic fracturing treatments. In traditional hydraulic fracturing treatments, a treatment fluid, sometimes called a carrier fluid in cases where the treatment fluid carries particulates entrained therein, is pumped into a portion of a subterranean formation (which may also be referred to herein simply as a “formation”) above a fracture gradient sufficient to break down the formation and create one or more fractures therein. The term “treatment fluid,” as used herein, refers generally to any fluid that may be used in a subterranean application in conjunction with a desired function and/or for a desired purpose. The term “treatment fluid” does not imply any particular action by the fluid or any particular component thereof. By way of non-limiting example, a “treatment fluid” may be an acidizing fluid, a fracture-initiating fluid, a proppant-laden fluid, etc. As used herein, the term “fracture gradient” refers to a pressure necessary to create or enhance at least one fracture in a particular subterranean formation location, increasing pressure within a formation may be achieved by placing fluid therein at a high flow rate to increase the pressure on the formation. Placing a fluid at a rate or pressure that is below the threshold to create or enhance at least one fracture is known as placing the fluid into the formation at “matrix flow rate.”
To achieve pressures above the fracture gradient, the treatment fluid is generally introduced at high pressures and/or high flow rates, which can cause turbulent flow of the treatment fluid. Such turbulent flow can result in friction pressure between the treatment fluid and subterranean formation equipment (e.g., wellbore piping, wellbore casing, and the like), as well as between the treatment fluid and the formation itself. Such friction pressure increases the energy necessary to pump the treatment fluid into the subterranean formation (e.g., the wellbore). Accordingly, friction reducing agents may be added to the treatment fluids to change the rheological properties of the treatment fluid to overcome or minimize the friction pressure.
Additionally, during stimulation operations, particulate solids are typically suspended in a portion of the treatment fluid and then deposited into the fractures, also increasing friction pressures. The particulate solids, known as “proppant particulates” or simply “proppant” serve to prevent the fractures from fully closing once the hydraulic pressure is removed. By keeping the fractures from fully closing, the proppant particulates form a proppant pack having interstitial spaces that act as conductive paths through which fluids produced from the formation may flow. As used herein, the term “proppant pack” refers to a collection of proppant particulates in a fracture, thereby forming a “propped fracture.”